In article number 1901338, Bayrammurad Saparov and co-workers introduce a family of nontoxic all-inorganic halides Rb2CuX3 (X = Br, Cl), prepared by using high temperature and solution techniques. The materials exhibit one-dimensional crystal structures and show high photoluminescence quantum yield blue emission up to unity attributed to self-trapped excitons. Single crystals of Rb2CuCl3 have also been shown to demonstrate an up-conversion photoluminescence, the first example of such behavior for a Pb-free metal halide.